In accordance with a common design in engine lubricating oil pumps, the oil delivered by the pump, i.e. the oil from the high-pressure side of the oil circulation supplied by the pump, is applied to an adjusting member which is used to influence the delivery volume, such as for example a setting ring which can be pivoted. In this way, the delivery volume flow is limited when a particular pressure threshold is reached. Depending on the ancillary constraints of the engine, such as for example the rotational speed of the engine, the temperature of the engine, the need to cool pistons and so forth, an adjustment of the delivery volume—preferably, the specific delivery volume—is often implemented in the form of two or as applicable even more pressure stages, wherein it is alternatively or additionally possible to regulate the pump in accordance with an engine characteristic map, i.e. to perform characteristic-map regulation. In simple cases, pressure can be directly applied to the adjusting member using a manifold valve which is actuated by the engine controller. If the electromagnetically operable manifold valve cannot be arranged in or on a housing of the pump and/or if, for design reasons, the flow cross-sections in the valve or on the route to or from the valve cannot be dimensioned so as to be sufficient for rapid adjustment, a hydraulic valve can be provided which controls the application of pressure to or relief of pressure on the adjusting member which can commonly be moved against the force of a spring. At least in such embodiments, a pressure which acts on a partial surface of a pilot piston of the hydraulic valve, which is typically embodied as a stepped piston, is modulated using the manifold valve which can be electromagnetically actuated.
WO 2006/066405 A1, which is incorporated by reference, discloses a pump comprising an adjusting member which can be adjusted back and forth in order to adjust the delivery volume and to which a setting pressure is applied in a setting direction in each of two setting chambers. A spring device acts on the adjusting member, counter to the setting pressures, in a restoring direction. In the first setting chamber, a setting fluid which is diverted from the high-pressure side of the pump is directly applied to the adjusting member. The setting pressure which prevails in the second setting chamber can be adjusted by means of an electromagnetic valve. It is also mentioned in relation to the first setting chamber that in modified embodiments, the setting pressure of the first setting chamber could alternatively also be adjusted by means of an electromagnetic valve.
WO 2008/037070 A1, which is incorporated by reference, discloses a pump comprising an adjusting member which can be adjusted in order to adjust the delivery volume and to which a first setting pressure is applied in a setting direction in a first setting chamber and to which a second setting pressure is applied in a setting direction in a second setting chamber. A spring device acts in the restoring direction, counter to the setting pressures. A fluidically operable valve is connected upstream of each of the two setting chambers, in order to be able to alter the setting pressure of the respective setting chamber. Setting fluid diverted from the high-pressure side of the pump is fed to each of the fluidically operable valves. The setting fluid can be fed via the valves of the respectively assigned setting chamber or can be drained into a reservoir. One of the two valves is directly operated using a control fluid diverted from the high-pressure side of the pump. The other of the two valves is fluidically operated by means of an electromagnetic valve.